1. Field of the Invention
The present invention relates to an analog-to-digital conversion apparatus that corrects digital data output from a plurality of analog-to-digital conversion units and a program therefor.
2. Description of Related Art
Conventionally, when converting an analog signal into an digital signal, there is known an N-phase (N-way) interleaved analog-to-digital conversion method using N analog-to-digital converters (hereinafter, referred to as ADCs) in order to raise a sampling rate apparently.
However, in the interleaved analog-to-digital conversion method as described above, when some errors are observed in phases of sampling clocks being supplied to each of ADCs and a frequency characteristic of each of ADCs, a frequency spectrum of a digital signal cannot be computed with high precision.
For example, phases of sampling clocks being supplied to each of ADCs have to be different from one another by a predetermined phase. However, it is difficult to move a phase of each of sampling clocks by a predetermined phase precisely. Moreover, although sampling clocks are supplied to each of ADCs with a precise phase, when a frequency characteristic of ADC is not ideal, a variation is observed in the sampling timing and again in each of ADCs and thus it is difficult to compute a frequency spectrum of a digital signal with high precision.
For this reason, it is necessary to correct the sampled digital signal according to a frequency characteristic of each ADC. For example, a method for correcting a spectrum transformed from the digital signal by way of discrete Fourier transform according to a frequency characteristic of each ADC is considered.
In this case, an arithmetic unit that conducts discrete Fourier transform and correction arithmetic sequentially acquires digital signal data by a predetermined data number and performs arithmetic processing. However, since the digital signal data are separately processed, there has been a problem that it is not possible to hold a continuity of a waveform of a digital signal.
Therefore, it is an object of the present invention to provide an analog-to-digital conversion apparatus and a program that can solve the foregoing problems. The above and other objects can be achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.